The World Health Organization warned on Wednesday that a global flu pandemic was imminent, raising its threat level as the swine flu virus spread and killed the first person outside of Mexico, a toddler in Texas.

Influenza pandemics must be taken seriously precisely because of their capacity to spread rapidly to every country in the world, WHO Director General Margaret Chan told a news conference in Geneva.

The biggest question is this: how severe will the pandemic be, especially now at the start, Chan said, but added the world is better prepared for an influenza pandemic than at any time in history.

Nearly a week after the H1N1 virus, or swine flu, first emerged in California and Texas and was found to have caused deaths in Mexico, Spain reported the first case in Europe of swine flu in a person who had not been to Mexico, illustrating the danger of person-to-person transmission.

Chan raised the WHO alert level to Phase 5, its second highest warning that a pandemic, or global outbreak of a serious new illness, is imminent.

The new alert a signal to governments and businesses to take action, and to pharmaceutical companies to ramp up antiviral drug production and capacity, she said.

Almost all cases outside of Mexico have had only light symptoms, and only a handful of cases have needed hospitalization.

But in Mexico, where up to 159 people have died from the virus and around 1,300 more are being tested for infection, people struggled with an emergency that has brought normal life virtually to a standstill over the past week.

I'm depressed. I don't understand where this came from, how it spreads, how long it will last or what it will to the economy, an elderly woman named Licha said, sitting on a Mexico City park bench and wearing a surgical mask.

MORE COUNTRIES, MORE CASES

Germany and Austria reported cases of the illness, bringing the number of affected countries to 9.

U.S. officials said a 22-month-old boy had died in Texas -- the first confirmed U.S. swine flu death -- while on a family visit from Mexico. Officials warned more deaths could be expected as surveillance of the illness increases.

President Barack Obama, facing the sudden flu emergency along with his broader drive to pull the United States out of its deep recession, said the Texas death showed it was time to take utmost precautions.

About 30 U.S. Marines in southern California on the biggest military base in the United States were quarantined after one of them was confirmed to have contracted the illness.

Despite jitters, many global markets rose as traders sought hopeful signs through the gloom of the worldwide financial crisis.

The market doesn't seem to be affected by this too much, said Cleveland Rueckert, market analyst at Birinyi Associates Inc. Stamford, Connecticut.

WORRIES FOR MEXICO

Mexico's central bank warned that the outbreak could deepen the recession, hurting an economy that already shrank by as much as 8 percent in the first quarter.

France said it would seek a European Union ban on Thursday on flights to Mexico. Argentina and Cuba have stopped flights from Mexico, and Ecuador restricted charters to and from the country.

The EU, the United States and Canada have advised against non-essential travel to Mexico, a popular tourist destination, with many of the cases linked to travel there.

H1N1 swine flu is seen as the biggest risk since H5N1 avian flu re-emerged in 2003, killing 257 people of 421 infected in 15 countries. In 1968 a Hong Kong flu pandemic killed about 1 million people globally, and a 1957 pandemic killed about 2 million.

Around the world, governments have built up stockpiles of two antiviral drugs -- Relenza, made by GlaxoSmithKline and Tamiflu, made by Roche AG and Gilead Sciences Inc..

Seasonal flu kills 250,000 to 500,000 people in a normal year, including healthy children in rich countries.

Health agencies advise frequent hand-washing and covering sneezes and coughs to help stop the spread. Experts generally agree that face masks, especially the surgical masks seen on the streets of Mexico City, offer little protection.